Thursday, June 30, 2011

Red Crossbill

A pair of Red Crossbills also fed at the Missoula bird feeder.  I was excited as, despite my banding many Red Crossbills,  I have mysteriously never photographed one. These photos are of the male, the female escaped my lens.  The curiously crossed bill is adapted as a conifer cone opener.

Birders have long recognized that Red Crossbills come in different sizes. One winter in Aberdeen I had a single flock of large and small crossbills visiting our feeder.  The size correlates with the size of the cones on which the birds feed.  Crossbills are nomadic and breed when a flock finds plenty the correct sized conifer cones.

Ornithologists next discovered that the different sized crossbills have distinct calls.  Furthermore, even when they breed in the same forest, birds with different calls do not interbreed.  Therefore we may have at least eight different species of red crossbills in North America!  Sibley's website discusses this situation and provides some interesting links.

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